Jet dissipation mechanisms on different scales

These days jets are observed on very different scales: from few gravitational radii to a few kiloparsecs. The variety of scales and variability times tells us that there are few dissipation mechanisms that transform electromagnetic energy into the observed radiation. In my talk I will discuss two possible mechanisms: (1) the energy dissipation in current sheets in the vicinity of the black hole and (2) the current-driven kink instability as a source of energy dissipation on the scales of 10^5-10^7 gravitational radii from the central engine.